Field
Various communication systems may benefit from the appropriate logging of measurements. For example, communication systems employing multimedia broadcast multicast service may benefit from logging multicast-broadcast single-frequency network measurements.
Description of the Related Art
Multimedia broadcast multicast service (MBMS) currently lacks fully agreed complete measurement definitions for the MBMS reception. Such definitions may need to take into account collection of multicast-broadcast single-frequency network (MBSFN) user equipment (UE) measurements with UE geographical location, to support verification of MBSFN actual signal reception and support planning and reconfiguration such as MBSFN areas and MBMS operation parameters selections. Furthermore, such definitions may need to specify MBSFN radio reception measurement(s) to be collected utilizing the third generation partnership project (3GPP) minimization of drive test (MDT) functionality
Currently agreed L1 measurements include the following: MBSFN reference signal received power (RSRP) and reference signal received quality (RSRQ) per MBSFN area, where MBSFN received signal strength indicator (RSSI) averaging is over only orthogonal frequency division multiplexed (OFDM) symbols carrying MBSFN reference signal (RS); and multicast channel (MCH) block error rate (BLER) measurement per modulation and coding scheme (MCS) per MBSFN area. In this, measurements are to be done only in sub-frames and carriers where the UE is decoding physical multicast channel (PMCH).
Specifications for signaling aspects, such as how the measurements are configured, reporting details, enhancements to the network interfaces and functions, and the like, have concluded that only logged measurements are supported, both in idle and connected. Additionally, current logged MDT principles for configuration and reporting will be re-used to large degree, such that configuration is done on a dedicated control channel (DCCH) using existing logged measurement configuration and the UE will indicate about the available log which is sent to network on request using UEInformationRequest/-Response signaling. According to these specifications, both management-based and signaling-based MDT may be used with the same principles as in legacy MDT.
The MBSFN transmission per MBSFN area conventionally consists of broadcasting, using SIB13, the allocation of MBMS control channel (MCCH),transmission of MCCH information such as MBSFN area configuration, including resource allocation for multicast traffic channel (MTCH), and transmission of MBMS traffic on MTCH. There is one MCCH per MBSFN area but there can be multiple services broadcast/multicast on a single MBSFN area.
The UE is conventionally supposed to regularly monitor the MCCH channel for any updated information. MCCH has a modification period and any content change is informed with a MBMS specific radio network temporary identifier (M-RNTI). The traffic is scheduled per MBMS scheduling period. The first MBMS sub-frame includes the MBMS scheduling information (MSI) which tell how the traffic for each active service is allocated within the MBMS scheduling period. Thus the scheduling can dynamically change from scheduling period to another. All this results in the MBSFN transmission having irregularity, which can impact how the UE can monitor and measure the PMCH.
The logged MDT measurement configuration conventionally defines the logging periodicity, namely how often the UE shall store measured results. The results are associated with a time and location information. The logging periodicity can be between 1 s and 61 s. With current logged MDT for radio resource management (RRM) related measurements, logged measurements are the latest available filtered measurement results for serving cell, neighbor cells or inter radio access technology (RAT) cells. The actual measurements are done just before the logging takes place.
With MBSFN reception, on the other hand, the situation is different due to the irregular and discontinuous nature of the measurement samples that the UE may get. Measurement time instants may be totally random with respect to the logging time instants. With long logging periodicities, the measurement time instants can be even tens of seconds before the logging is supposed to be done.
Further, the MDT log entry can be associated with the location information which should be related to the physical location where the measurement was done. This means that there is a limited validity time when the obtained location information is valid. If the measurement time instant deviates too much from the time a new location fix is obtained, accurate location information, from a stand-alone global navigation satellite system (GNSS) function such as global positioning system (GPS), is not stored. The available cell measurement results will provide information about coarse UE location.
For the RSRP/RSRQ measurement, the measurement period may be defined as follows: measurement contains at least 5 decoded MBSFN subframes with MCH (what the UE is receiving for the MBMS service of interest) or minimum measurement period is [640] ms.
The UE is conventionally only required to perform MBSFN measurements when the UE is otherwise required to decode the PMCH (MCCH and/or MTCH). The minimum requirements for the UE to monitor the PMCH is influenced by the network MBMS configuration (MCCH) and the network MBMS scheduling together with which MBMS services the UE is interested in and/or subscribed to.
UE monitoring only the MCCH (for example, when waiting for the MBMS service to start or being interested in receiving the MBMS service) the reception may happen infrequently as illustrated in FIG. 4. Specifically, FIG. 4 illustrates MCH reception when monitoring only MCCH.
If the minimum number of samples is five, the maximum duration of the measurement is 20.48 s: 4×5.12 s=4×mcch-ModificationPeriod/notificationRepetitionCoeff=20.48 s, where 5.12 s is the minimum that UE is to receive while monitoring only MCCH; mcch-ModificationPeriodp=1024 radio frames, notificationRepetitionCoeff=2.
Thus, 4 intervals may be needed to receive 5 samples. Therefore, the measurement period may span multiple logging periods (logging period can be 1.28 s, 2.56 s, 5.12 s, . . . , 61.44 s). This means that if the five samples for a single measurement result represents a sliding window and the logging is done once per logging period, successive measurement results can be highly correlated or even the same, such as when no new samples are received during the last logging period, see FIG. 5. Specifically, FIG. 5 illustrates MCH reception versus logging periods.
The details of how the UE shall perform the measurements have not yet been specified. For example, it has not yet been specified whether the UE shall use 5 samples applying a sliding window approach or whether the UE shall measure using a 5 sample window.